Perhaps we should insert humans in the loop, to verify whether useful work was performed.
Or some AI because humans are prone to bribery to some extent.
Or we could make it democratic. "Jeff Bezos asserts that he provided useful work for society and that he therefore deserves $1B this year. Please cast your votes".
PoW should actually stand for Proof of Waste. It's not even unprecedented in nature: many species will intentionally waste energy or resources to demonstrate mating fitness, as with a peacock's tail.
